Core box and molding assembly for internal combustion engine blocks



F eb. 7, 1967 2 3,302,250

J. L. FL! CORE BOX AND MOLDING ASSEMBLY FOR INTERN COMBUSTION ENGINEBLOCKS 65 3 Sheets-Sheet 1 Original Filed Dec. l8, l9

INVENTOR.

N i ld/z ATTORNEY Feb. 7, 1967 J, L Z 3,302,250?

CORE BOX AND LDING AS BLY FOR INTERNAL COM TION ENGI BLOCKS OriginalFiled Dec. 18, 1965 3 Sheets-Sheet 2 ATTORNFY J. L. FLITZ CORE BOX ANDMOLDING ASSEMBLY FOR INTERNAL Feb. 7, 1967 COMBUSTION ENGINE BLOCKS 65 3Sheets-Sheet 3 Original Filed Dec. l8, 19

FNVIINTOR.

W W P. m WW United States Patent 3,302,250 CORE BOX AND MOLDING ASSEMBLYFOR INTERNAL COMBUSTION ENGINE BLOCKS John L. Flitz, Saginaw, Mich.,assignor to General Motors Corporation, Detroit, Mich., a corporation ofDelaware Original application Dec. 18, 1963, Ser. No. 331,442, now

Patent No. 3,264,693, dated Aug. 9, 1966. Divided and this applicationApr. 27, 1966, Ser. No. 545,747

5 Claims. (CI. 2213) This is a division of the patent application S.N.331,- 442, filed December 18, 1963, now Patent No. 3,264,693.

This invention relates to sand casting internal combustion engineblocks, and more particularly to a core box for making an improved corearrangement whereby such engine blocks may be more accurately formedthan before.

Cast iron engine blocks are made in sand molds which are formed in metalflasks by ramming both the cope and the drag half with green sand arounda pattern. The two flask halves are then assembled together afterremoval of the patterns to establish a mold cavity which generallydefines the exterior surface configurations of the engine block. Bakedsand cores are supported in spacial relationship within the cavity bywires, core print projections, or the like to define the interiorsurfaces of the block.

Some of the more undesirable aspects of sand casting come from the sandcores which are required to define interior spaces of the engine block.To form a block as many as twenty such cores may be required, some coresbeing glued together and assembled with others until the requiredinterior shape is formed. Naturally a slight misalignment due to ashifting of sand cores being glued will be carried over as an error intothe finished casting; Furthermore, such interior cores often require theuse of support r-ods or cha-plets to locate them in the mold and toprevent them from being floated out of position due to the buoyancy ofthe molten iron. These chaplets are intended to become an integral partof the casting, but if the bond is defective the casting may leak.

Core setting is also a major problem. In simple castings, the cores maybe located by the core prints in the drag half of the mold, but in morecomplicated coring arrangements some sort of transfer fixture thatprepositions the core assembly prior to placing it in the mold isrequired.

In the past, cast iron blocks required considerable machining and wererelatively heavy units, not only due to the weight of cast iron, butalso due to the thick walls required to achieve a structurally soundpart.

The weight factor in the present day automobile has become such a sorepoint that lighter engine blocks have become attractive; hence there hasbeen a shift recently to emphasize the light weight metals, such asaluminum alloys, which may be pressure die cast. Such a process does notrequire sand cores and inherently overcomes many of the defectsheretofore plaguing the sand molding process. However, die casting ofaluminum alloys, or similar light metals, has its problems too due tothe high cost of equipment and the troublesome metallurgical propertiesof these metals; hence the most recent trend is now a shift back towardscast iron for making engine blocks.

This re-evaluation of the cast iron block has been possible primarilythrough recent improvements in core assembly techniques and mold andcore castings which allow more accurate, thin walled castings to bemade. The former technique is disclosed in United States Patent2,783,510, Dolza et al. In Dolza et al., the conventional projectionsand depressions embracing the interior surfaces of the block so that asingle core may be employed for each crankthrow compartment andassociated cylinder cavity, the crankcase-barrel core units being formedin a core box the parting line of which would be in an imaginary planepassing transversely through the block and generally through the axes ofthe cylinders. In other words, in the past where a separate core wasrequired for each cylinder barrel and crankthrow area, the crankcase andbar-rel cores may be formed according to Dolza et al. in one piece whilelying on their sides in a core box having a horizontal parting linethrough the center. A plurality of such crankcase and barrel core units,depending on the number of cylinders in the engine, can then beassembled, one behind the other, in the drag half of the mold with thevarious cooperating core elements arranged around them, thus greatlyreducing the number of cores required and simplifying the procedure ofcore setting. The core setting step may be even further improved by thetechnique shown in the United States Patent 2,768,- 414, Dolza, where ametal tray is used to prearrange the crankcase-barrel cores.

Due to the elimination of a great many core pieces and more accuratemeans for core setting, the accuracy of iron blocks has improved and thecost has been reduced. Following the trails blazed by Dolza in hispatents, the present invention makes a significant contribution andimprovement which it is believed makes sand casting even moreadvantageous for the manufacture of vehicle engine blocks.

In accordance with the present invention, a one piece crankcase-barrelcore for all of the crankthrow and cylinder bar-rel spaces in the blockis provided which comprises the basic core unit of an interfitting coreassembly. The crankcase-barrel core unit is formed in a novel multi-partcore box including a plurality of fixed and relatively movable sectionsadapted to define a core mold cavity when in the closed position andhaving blow tubes for introducing a core sand mixture into the cavityunder air pressure and vents for exhausting the cavity. The movablesections include a cover section with projections or blades adapted tobe withdrawn from the core interior to render inner adjacent surfacesthereof exposed for cooperation with surfaces in the mold cavity todefine the bulkhead and bearing structure of the engine block and areciprocative barrel section for forming the barrel core portionsmovable relative to the cover section along the axes of the barrel coreportions of the crankcase-barrel core unit.

Additional features and objects of this invention will be made clear byreference to the following detailed description and drawings wherein:

FIGURE 1 is an exploded perspective view of the one piececrankcase-barrel core showing it and other cores used to form a V-8cylinder block for an internal combustion engine and the relationship ofthese cores with each other in accordance with the present invention;

FIGURE 2 is a perspective view of the drag and drag half of the moldshown ready to receive the core assembly in FIGURE 1; 1

FIGURE 3 is a perspective view of the drag shown in FIGURE 2 with thecore assembly in place;

FIGURE 4 is a sectional view taken along the line 44 of FIGURE 3 throughthe mold with the cope in place showing the spacing of the core assemblyin the mold;

FIGURE 5 is a sectional view of the core box for making the one piececrankcase-barrel core shown in the closed position; and

FIGURE 6 is an exploded perspective view of the movable core boxsections.

Referring to FIGURES 1-4, a five-piece baked sand core assembly isprovided which includes a unitized crankcase-barrel core 10,. right andleft water jacket cores 12 and 13, a rear end core 14, and a front endcore 16. The core assembly is positioned in the casting cavity of thedrag half of the sand mold 18 shown in FIGURE 2 and having a bottom wallin which is formed a longitudinally extending elongated portion 20 whichdirectly supports the crankcase-barrel core and rear and front cores 14and 16. The portion 20 is positioned to support the core assembly inspacial relationship within the mold cavity when the flask is closed andis formed along with the drag half of the mold in the conventionalmanner by ramming green sand around a pattern having the shape of thedrag cavity which defines the lower exterior walls of the block. Afterthe drag half of the mold 18 has been rammed, the cope half 24 shown inFIGURE 4, is likewise rammed with green sand about a pattern forming thecope cavity defining the upper exterior block walls. The core assembly10, 12, 13, 14, and 16 is then positioned in the drag cavity as shown inFIGURE 3 whereupon the cope half of the mold 24 is assembled closing themold, proper positioning of the cope and drag being insured by the flaskpins 26 for purposes of illustration, the pins 26 are shown at eachcorner of the drag and are to be received in holes at each corner of thecope, however, in practice, a metal flask of more conventional designwould be used. With the flask closed as viewed in FIGURE 4, it is readyto receive molten metal to start the casting process.

Referring in more detail to FIGURE 1, the crankcasebarrel core unitshown is adapted for use in casting a 90 eight cylinder internalcombustion engine. Obviously the type of engine or the number ofcylinders is not a limitation to this invention, and the concepts hereofcan be readily adapted by modifying the core assembly for use in makinga V-6 or even an inline engine block. The core 10 being for a V-typeengine has a plurality of alinged core body portions 27 of generallytriangular shape appropriate to define the crankthrow areas below theengine cylinders. The engine cylinders are cored by the integrallyformed barrel core portions 28 and 29 projecting from the triangularside walls 30 of the body portions 27 forming left and right inclinedparallel rows. In this case, the left barrel core portions 28 arearranged in a V-fashion at 90 to the right barrel core portions 29. Thebarrel core portions have conical bores 31 the function of which will bedescribed hereinafter. The body portions 27 are not separate units butare formed together as a unitary member having generally verticallyextending recesses bounded by inneradjacent laterally extendingtransverse surfaces 32 and being joined locally at the corners by thelongitudinally extending leg portions 34 on either side at the bottomand by the cam shaft gallery core portion 35 at the top. The inneradjacent walls or surfaces 32 of the body portions=27 cooperate with theslab 20 in the drag half of the mold 18 to define the bulkhead andbearing structure of the engine block. Accurate portions 36 at the basesof the body portions 27 mate with the longitudinally extending crown 37of the slab 20 to confine the molten metal within the spaces betweenthe-adjacent body portions 27. When the main core 10 is assembled withthe end cores 14 and 16, the end walls of' the outer core body portions27 will be spaced from the inner walls of the end cores by coreprojections such as 38 on the front core 16, this projection forming thecam shaft opening in the front wall of the block. A similar projection(not shown) on the rear core 14 is also provided. The spacing betweenthe cores 10, 14, and 16 will be sufficient to define the end Walls ofthe block while the triangular side walls 30 of the body portions 27will form the interior right and left bank walls of the upper crankcaseregion through which the cylinders open. The rear core 14 has a recess39 which partially surrounds the vertical projection 40 on the core 10being spaced sufficiently therefrom to form a distributor boss in thetop of the block.

The water jacket cores 12 and 13 are assembled over the barrel portions28 and 29 of the core 10 and include generally cylindrical body portions42 having interior cylindrical walls 43 which are of larger dimensionthan the barrel portions 28 and 29 so that when arranged in coaxialrelationship therewith there will be a radial spacing between them. Thisradial spacing, which conforms to the engine cylinder barrels, isestablished by virtue of the core straps 44 and depending posts 45 whichmate with the conical bores 31 of the barrel core portions as best seenin FIGURE 4. A fit of the posts and bores is reached when the tops ofthe barrel core portions abut against the undersurface of the straps 44automatically locating the water jacket cores in spacial relationshipwith respect to the crankcase-barrel core unit 10. A core locatingfunction is also performed by the core bosses 46 which project from thelower sides of the cylindrical portions 42 and bear against the inclinedgreen sand walls 47 of the drag. These bosses form openings in thefinished casting that are closed by sheet metal plugs in the well-knownmanner. Passages 48 opening at the top of the straps 44 extend down intothe posts 45 opening at the other end within the bores 31 to vent thecore 10 through passages 49 in the cope.

This arrangement of locating the water jacket cores for a V-type enginecore assembly is a departure from the past practice taught, for example,by the Dolza et a1. patent. There a plurality of metallic spacer sleevesare used to properly space the water jacket cores from the barrel coreportions. These sleeves are preferably slightly conical in shape andtheir smallest internal diameters are somewhat smaller than the outsidediameter of the barrel portions. Thus when the spacer sleeves areassembled over the barrel portions, the outward taper of their innersurfaces prevents their sliding downward on the barrel portions to anexcessive extent with the result that their lower edges arespaciallyseparated from the sloping side surfaces of the body portionsof the crankcase-barrel cores. When the spacer sleeves are securely inposition around the barrel portions, the two water jacket cores areplaced over the sleeves and the barrel portions so that the latterprotrude completely through the openings formed by the cylindrical bodyportions of the water jacket core. After assembly of the cores in thedrag, the spacer sleeves are then removed since the positioning of thewater jacket cores with respect to the barrel core portions is nowmaintained by core prints in the mold.

In the present invention, the need for metallic spacer sleeves iseliminated, and instead this function is performed by the integrallyformed core straps 44 and posts 45. It may be appreciated that theradial spacing of the water jacket core is extremely critical since aslight misalignment will cause a thin metal region to form between thecylinder barrel and the water jacket possibly resulting in a crack inthe cylinder wall during operation leading to total engine failure. Withthe present water jacket positioning, the posts 45 extend far enoughinto the barrel bores 31 to give stability to the whole water jacketcore along the axis of the cylinder barrels during the casting processwhich was not the case in the past practice where the metallic spacersleeves were removed prior to metal being poured. In that arrangementWhile the metal was being poured, the positioning of the water jacketcores depended primarily upon the core prints formed in the drag whenramming the sand around the pattern. It might be appreciated that slightpattern wear in the area of these core prints may cause a considerableerror to be introduced with the result that the water jacket cores wouldbe allowed to float out of position slightly. Also the use of a largenumber of metallic chaplets to reduce the tendency of the cores to floathas been common practice.

To eliminate these causes of poor castings and to facilitate coresetting in the invention, the dependency on green sand core prints isreduced and the use of chaplets is also reduced. For example, the frontend core 16 has core print recesses, 50 on opposite sides thereof toreceive the core projections 51 formed on the ends of the water jacketcores. Hence there is no problem of trying to match green sand coreprints in the drag up with separate core projections when setting thecore assembly where in the Past, a number of core projections wereseated in the drag and had to be aligned individually when placing thecore assembly. Proper longitudinal positioning of the core assembly 10,12, 13, 14, and 16 in the drag 18 is insured by the core print 52 in thegreen sand on the left side of the drag wall which cooperates with asmall projection (not shown) on the left leg 34 of the crankcase-barrelcore to locate the entire core assembly with respect to the drag cavity,the recesses 54 and 56 in the drag being shaped to receive the end cores14 and 16 respectively. The flask pins 26 serve to locate the cope overthe drag; and with the flask in the closed position, as shown in FIGURE4, ready to receive molten metal, it is seen that the straps 44 engagesurfaces in the cope to prevent floating of the cores during casting.

Spruce openings 58 (not shown) extend from the top of the flask downthrough the cope and drag, cooperating in the drag with channels 59 inthe back side of the rear core 14 and the channels 58 in the drag 18 toopen into the longitudinal runners 60 formed in the drag below each leg34 of the crankcase-barrel core 10. As seen in FIGURE 4, gates 62 on theinner edges of the runners 60 open upwardly into the spaces betweenadjacent body portions 27 and between the end cores 14 and 16 and core10 permitting molten metal to rise into the mold cavity at the enginebulkhead and end wall locations. The gate and runner system is rammed upwith the green sand of the drag.

As taught by the Dolza et al. patent, separate crankcase-barrel coreunits for a V-type engine block are arranged one behind the other in thedrag, being mutually spaced from one another by integrally formed coreprojections which engage the rear surface of the immediately precedingcrankcase-barrel core thereby defining the lower surfaces of the enginebulkheads. These crankcasebarrel cores must be separately formed lyingon their sides in -a core box having a parting line in a plane passinghorizontally through the center. Since the core box opens in -adirection normal to this plane and each crankcase-barrel core is aseparate unit, it is possible therefore to form the bulkhead bottomsurface core projections on the sides of the body portions normal to theparting line.

It is important to note that in the present invention thecrankcase-barrel core 10 is a one piece construction in which eachbulkhead of the engine is defined in the space between adjacent bodyportion 27 and the green sand of the rammed portion 20 in the drag. Acore box of the type used to form the separate crankcase-barrel coreunits in Dolza with the parting plane passing generally through the axesof the cylinders could not be used to manufacture the core 10 for thereason that a plurality of body portions and integral barrel portions27, 28, and 29 are all joined together as a unit, one behind the otherin aligned fashion.

To deal with the problem of manufacturing an integrated crankcase-barrelcore such as that shown in FIG- URE 1, I have developed the novel corebox illustrated in FIGURES 5 and 6 which includes a plurality of corebox sections, some of which are movable with respect to others which arefixed; the movable sections moving relative to each other and to thefixed sections to define a closed cavity of the configuration of thecore 10 as shown in FIGURE 5.

Referring to FIGURES, the core box 70 is shown in the closed positionand includes a vertically movable cover section 72 positioned above afixed base section 74 which provides a surface 75 to support obliquelyslidable barrel forming side sections 76 and a mold surface 89 forforming a portion of the camshaft gallery oore portion 35. The sidesections 76 have longitudinal bearing surfaces 78 which mate withcomplementary bearing surfaces 79 on the cover section in the closedposition to lock the movable sections in a closed position. Stripperplates 80 fixed to the base section 74 extend parallel to the backsurfaces 82 of the side sections 76 and are spaced therefromsufficiently to be out of range when the side sections are moved to theopen position. The back surfaces 82 have a plurality of ports 84 whichare aligned with ports 85 in the tops of the barrel forming molds 86.The aligned ports 84 and 85 are adapted to receive ejection pins 88mounted on the fixed stripper plates '80.

Bl-ow tubes 90 formed in a cover section 72 communicate with the sandhopper of a standard core blowing machine for introducing the core sandmixture into the mold cavity under air pressure, filling the cavity withtightly packed core sand. The air pressure is exhausted through airvents (not shown) in the right and left barrel molds and the basesection. As seen by inspection, the core 10 is formed upside down in thecore box which may then be shuttled over gas burners heating the corebox and core sand mixture to the baking temperature. After baking, thecore box is opened by raising the cover section 72 and retracting rightand left barrel forming sections 76 relative to the ejection pins 88which are stationary and extend into the barrel forming molds 86 asshown in FIGURE 6.

The relative positions of the movable core box sections are best shownin FIGURE 6 where the barrel forming side sections 76 have been moveddownwardly and outwardly relative to the top section 72 which has beenpreviously raised vertically. Of course to closed the box, the sequenceis merely reversed; that is, the side sections are first moved to theclosed position and then the cover section is lowered.

The core box projections on the cover section 72 form the interiorspaces of the main core 10 and include the blades 92 which define thecore spaces between the body portions 27, such spaces forming thebulkhead and bearing regions of the engine block. The point here is thatno core projections can be allowed on the inner adjacent surfaces 32 ofthe main core 10 since this would interfere with the pulling of theblades 92 from between such surfaces. In addition, some redesigning ofthe engine bulkhead construction is necessary in order to take intoaccount the fact that there must be sufficient draft in the surfaces 32in order to pull the blade projections.

In other words, the inner adjacent side surfaces 32 must open downwardlyand outwardly with respect to a transverse plane which is the plane ofthe cross section in FIGURE 5 but passing generally through the centerof the bulkhead spaces. This is one way of saying that these surfacesmust be free of any projections or pockets and re-entrant angles whichwould otherwise prevent the pulling of the core box projections. Withthe design of the engine accordingly modified, as dictated by thefoundry practice disclosed here, it is now possible to join the corebody portions and barrel core portions into a one piece crankcase-barrelcore unit.

Having now described the invention in its preferred embodiment and insuflicient detail to allow the same to be practiced, it is intended thatobvious changes may be made, such as modifying the invention toaccommodate engine blocks having a different number of cylinders or thelike, without deviating therefrom as defined in the appended claims.

I claim:

1. A multi-part core box adapted for use in making a sand core of thetype suitable for use in casting the interior crankcase and cylinderbarrel surfaces of a V-type internal combustion engine frame,

said core having a crankcase forming body portion which supportsintegrally formed barrel core portions projecting therefrom in inclinedV-fashion, said core box including fixed and relatively movable core boxsections cooperating in a closed position to define said core moldcavity, means associated with one of said sections for admitting a coresand mixture under fluid pressure into the cavity, said movable sectionscomprising:

a movable cover section having molding projections thereon for formingthe core surfaces of the body portion used for defining the bulkheadsurfaces of the engine frame; and

obliquely movable side sections mutually closable with said coversection having mold cavities therein for forming said barrel coreportions.

2. A multi-part core box adapted for use in making a sand core of thetype suitable for forming the interior crankcase and cylinder barrelsurfaces of a cast V-type internal combustion engine frame, said corehaving integrally formed triangular body portions being locally spacedapart to expose inner adjacent side surfaces thereof, said body portionssupporting integrally formed barrel core portions projecting from thetriangular side surfaces thereof in inclined V-fashion, said core boxincluding fixed and relatively movable sections cooperating in a closedposition to define said core mold cavity, means for introducing a coresand mixture under fluid pressure into the mold cavity associated withone of said sections, said movable sections comprising:

a vertically movable cover section having molding projections thereonfor forming said inner adjacent side surfaces of the core body portionsused for defining the bulkhead surfaces of the engine frame; and

downwardly and outwardly movable side sections having mold cavitiestherein for forming said barrel core portions, said side sections beingmovable in the axes of said barrel core portions between closed and opencavity portions with respect to the vertical displacement of said coversection.

3. Claim 1 wherein said movable cover section includes opposed inwardlyfacing bearing portions and said obliquely movable side sections eachinclude an outwardly facing bearing portion which is adapted to matewith the said inwardly facing bearing portions whereby said obliquelymovable side sections are locked in place by said cover section when thesaid movable portions are in a closed position.

4. A multi-part core box adapted for use in making a sand core of thetype suitable for use in casting the interior crankcase and cylinderbarrel surfaces of a V- type internal combustion engine frame, said corehaving a crankcase forming portion which supports integrally formedbarrel core portions projecting therefrom in inclined V-fashion and acamshaft gallery forming core portion,

said core box including fixed and relatively movable core box sectionscooperating in a closed position to define said core mold cavity, saidfixed core box section including a mold surface for defining a portionof said camshaft gallery core portion, said movable sections comprisinga movable cover section having molding projections thereon for formingthe core surfaces of the body portion used for defining the bulkheadsurfaces of the engine frame and obliquely movable side sectionssupported by said fixed portion mutually closable with said coversection having mold cavities therein for forming said barrel coreportions. 5. Claim 4 wherein said fixed core box section and saidobliquely movable side sections cooperate to define said gallery coreportion.

References Cited by the Examiner UNITED STATES PATENTS 2,768,414 10/1956Dolza 22131 X 2,831,225 5/1958 Kolbe et al 22131 1. SPENCER OVERHOLSTER,Primary Examiner.

E. MAR, Assistant Examiner.

1. A MULTI-PART CORE BOX ADAPTED FOR USE IN MAKING A SAND CORE OF THETYPE SUITABLE FOR USE IN CASTING THE INTERIOR CRANKCASE AND CYLINDERBARREL SURFACES OF A V-TYPE INTERNAL COMBUSTION ENGINE FRAME, SAID COREHAVING A CRANKCASE FORMING BODY PORTION WHICH SUPPORTS INTEGRALLY FORMEDBARREL CORE PORTIONS PROJECTING THEREFROM IN INCLINED V-FASHION, SAIDCORE BOX INCLUDING FIXED AND RELATIVELY MOVABLE CORE BOX SECTIONSCOOPERATING IN A CLOSED POSITION TO DEFINE SAID CORE MOLD CAVITY, MEANSASSOCIATED WITH ONE OF SAID SECTIONS FOR ADMITTING A CORE SAND MIXTUREUNDER FLUID PRESSURE INTO THE CAVITY, SAID MOVABLE SECTIONS COMPRISING:A MOVABLE COVER SECTION HAVING MOLDING PROJECTIONS THEREON FOR FORMINGTHE CORE SURFACES OF THE BODY PORTION USED FOR DEFINING THE BULKHEADSURFACES OF THE ENGINE FRAME; AND OBLIQUELY MOVABLE SIDE SECTIONSMUTUALLY CLOSABLE WITH SAID COVER SECTION HAVING MOLD CAVITIES THEREINFOR FORMING SAID BARREL CORE PORTIONS.